Contact management for mobile communication devices in wireless packet switched networks

ABSTRACT

Methods and apparatus for efficient communications in a wireless communication network are provided. The wireless communication network has a predetermined network paging pattern which includes a plurality of page transmission periods during which repeated attempts for initiating a communication with a mobile communication device are made until the communication is established, if at all. The mobile device attempts to decode information over a wireless communication channel during each one of the page transmission periods. If the information is unsuccessfully decoded during all of the page transmission periods, the mobile device causes a message which informs the network of the mobile device to be transmitted to the wireless network. On the other hand, if the information is successfully decoded during at least some, but not all, of the page transmission periods, the mobile device refrains from transmitting the message to the wireless network.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and is a continuation of U.S.non-provisional patent application having application Ser. No.11/215,335 and filing date of 30 Aug. 2005, now U.S. Pat. No. 7,373,145,which is a continuation of U.S. non-provisional patent applicationhaving application Ser. No. 10/491,321 and filing date of 31 Mar. 2004,now U.S. Pat. No. 6,999,729, which is a National Stage filing of PCTapplication having application number PCT/CA02/01472 and internationalfiling date of 27 Sep. 2002, which claims earlier priority to U.S.provisional patent application having application No. 60/325,545 andfiling date of 1 Oct. 2001, each of which are hereby incorporated byreference herein.

BACKGROUND

1. Field of the Technology

The present disclosure relates generally to the field of wirelesscommunications, and in particular to techniques for improving thetimeliness in which data packets are delivered to a mobile device over awireless link in marginal coverage without adding undue amounts ofpolling across the link.

2. Description of the Related Art

Mobile communication devices, when operating within fringe coverageareas in wireless packet switched networks, may only be able to send andreceive packet traffic during sporadic intervals. This causesconventional notions of packet-switched data transactions to break down.Conventional approaches, such as simply retrying transmissions using aback off algorithm, will result in either an intensive use of radioresources (e.g. excessive polling) or poor reliability, especially forcommunications in a direction from the network to the mobile device. Inmarginal coverage, data may not be received at the mobile device in atimely fashion as is expected for real-time applications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a communication system in which thetechniques of the instant application may be implemented;

FIG. 2 shows a mobile device state transition diagram in accordance withvarious aspects of the techniques of the instant application;

FIG. 3 is a block diagram of a preferred communication system with whicha network update scheme according to the instant application may beimplemented;

FIG. 4 is a block diagram of a preferred mobile communication devicewhich may be configured to inform a network of its connection status inaccordance with a network update scheme described in this application;

FIG. 5 is a flowchart which describes one method of maintaining contactwith a wireless network;

FIG. 6 is a flowchart which describes another method of maintainingcontact with a wireless network;

FIG. 7 is a flowchart which describes yet another method of maintainingcontact with a wireless network; and

FIGS. 8(A)-(G) are timing diagrams related to the method described inrelation to FIG. 7.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Methods and apparatus for efficient communications in a wirelesscommunication network are described herein. The wireless communicationnetwork has a predetermined network paging pattern which includes aplurality of page transmission periods during which repeated attemptsfor initiating a communication with a mobile communication device aremade until the communication is established, if at all. The mobiledevice attempts to decode information over a wireless communicationchannel during each one of the page transmission periods. If theinformation is unsuccessfully decoded during all of the pagetransmission periods, the mobile device causes a message which informsthe network of the mobile device to be transmitted to the wirelessnetwork. On the other hand, if the information is successfully decodedduring at least some, but not all, of the page transmission periods, themobile device refrains from transmitting the message to the wirelessnetwork.

FIG. 1 is a block diagram of a communication system in which thetechniques of the instant application may be implemented. The exemplarycommunication system 300 includes a network 302 and a mobilecommunication device 304 which communicate over a wireless link 305.Network 302 includes a server 306, a network controller 308, a basestation controller 310, a base station 312, and an antenna shown in FIG.1 to include an antenna tower 313.

Server 306 may be any component or system connected within or to network302. For example, server 306 may be a service provider system whichprovides wireless communication services to device 304 and stores datarequired for routing a communication signal to the mobile device 304.Server 306 may also be a gateway to other networks, including but in noway limited to a telephone network, a local area network, or a wide areanetwork, such as the Internet. Those skilled in the art to which theinstant application pertains will appreciate that although only a singleserver 306 is shown in FIG. 1, a typical communication network mayinclude further additional network storage, processing, routing andgateway components.

Network controller 308 normally handles routing of communication signalsthrough network 302 to a destination mobile communication device (suchas mobile device 304). In the context of a packet-switched communicationnetwork, such as a General Packet Radio Service (GPRS) based network,network controller 308 must determine a location or address of thedestination mobile device and route packets for the mobile devicethrough one or more routers or switches (not shown) and eventually to abase station (such as base station 313) serving a network coverage areain which the mobile device is currently located.

Base station 312 and its associated controller 310 and antenna/tower 313provide wireless network coverage for a particular coverage areacommonly referred to as a “cell”. Base station 312 transmitscommunication signals to and receives communication signals from mobiledevices within its cell via antenna 313. Base station 312 normallyperforms such functions as modulation and possibly encoding and/orencryption of signals to be transmitted to the mobile device inaccordance with particular, usually predetermined, communicationprotocols and parameters, under the control of base station controller310. Base station 312 similarly demodulates and possibly decodes anddecrypts, if necessary, any communication signals received from mobiledevice 304 within its cell. Communication protocols and parameters mayvary between different networks. For example, one network may employ adifferent modulation scheme and operate at different frequencies thanother networks.

Those skilled in the art will appreciate that an actual wirelessnetwork, such as a Mobitex™ network or a DataTAC™ network, for example,may include hundreds of cells, each served by a distinct base stationcontroller 310, base station 312 and transceiver, depending upon thedesired overall expanse of network coverage. All base stationcontrollers and base stations may be connected by multiple switches androuters (not shown), controlled by multiple network controllers, onlyone of which is shown in FIG. 1. Similarly, as described above, network304 may also include a plurality of servers 306, including for examplestorage, routing, processing and gateway components. Mobitex™ is aregistered trademark of Telia AB; and DataTAC™ is a registered trademarkof Motorola, Inc.

Thus, the term “network” is used herein to denote the fixed portions ofthe network, including RF transceivers, amplifiers, base stationcontrollers, network servers, and servers connected to the network.Those skilled in the art will appreciate that a wireless network may beconnected to other systems, possibly including other networks, notexplicitly shown in FIG. 1. A network will normally be transmitting atthe very least some sort of paging and system information on an ongoingbasis, even if there is no actual packet data exchanged. Although thenetwork consists of many parts, these parts all work together to resultin a certain behaviour at the wireless link. However, which parts of thenetwork are responsible for which particular aspects of the finalbehaviour over the wireless link is beyond the scope of thisapplication. What is important is the overall behaviour that thecomponents of the network produce, as described in further detail below.

Mobile communication device 304 preferably has a display 320, a keyboard322, an possibly one or more auxiliary user interfaces (UI) 324, each ofwhich are coupled to a controller 314, which in turn is connected to amodem 316 and an antenna 318. Mobile communication device 304 sendscommunication signals to and receives communication signals from thenetwork 302 over wireless link 305 via antenna 318. Radio modem 316performs functions similar to those of base station 312, including forexample modulation/demodulation and possibly encoding/decoding andencryption/decryption. It is also contemplated that modem 316 mayperform certain functions in addition to those that are performed bybase station 312. Where the information in a communication signal orpacket is confidential and can be decrypted only at a destination mobiledevice, for example, base station 312 may not encrypt a received packetwhich contains information that has been previously encrypted, whereasthe radio modem may decrypt such encrypted information. It will beapparent to those skilled in the art that the radio modem will beadapted to the particular wireless network or networks in which themobile device 304 is intended to operate.

In most modern communication devices, controller 314 will be embodied asa central processing unit or CPU running operating system software whichis stored in a mobile device memory component (not shown). Controller314 will normally control overall operation of the mobile device 304,whereas signal processing operations associated with communicationfunctions are typically performed in the modem 316. Controller 314interfaces with device display 320 to display received information,stored information, user inputs and the like. A keyboard 322, which maybe a telephone type keypad or full alphanumeric keyboard, possibly withauxiliary input components, is normally provided on mobile communicationdevices for entering data for storage on the mobile device, informationfor transmission from the mobile device to the network, a telephonenumber to place a call from the mobile device, commands to be executedon the mobile device, and possibly other or different user inputs.

Thus, the term “mobile device” is used herein in reference to a wirelessmobile communication device. The mobile device may consist of a singleunit, such as a data communication device, a cellular telephone, amultiple-function communication device with data and voice communicationcapabilities for example, a personal digital assistant (PDA) enabled forwireless communication, or a computer incorporating an internal modem,but may instead be a multiple-module unit, comprising a plurality ofseparate components, including but in no way limited to a computer orother device connected to a wireless modem. In the mobile device blockdiagram of FIG. 1 for example, modem 316 and antenna 318 may beimplemented as a radio modem unit that may be inserted into a port on alaptop computer, which would include display 320, keyboard 322, possiblyone or more auxiliary UIs 324, and controller 314 embodied as thecomputer's CPU. It is also contemplated that a computer or otherequipment not normally capable of wireless communications may be adaptedto connect to and effectively assume control of the radio modem 316 andantenna 318 of a single-unit device such as one of those describedabove. Although only a single device 304 is shown in FIG. 1, it will beobvious to those skilled in the art to which this application pertainsthat many devices, including different types of devices, may be activeor operable within a wireless communication network at any time.

Having described the components within the system of FIG. 1, itsoperation will now be discussed in further detail. A mobile devicetransmitter, within the radio modem 316 in FIG. 1, is typically keyed orturned on only when it is sending to the network, and is otherwiseturned off to conserve resources. Such intermittent operation of thetransmitter has a dramatic effect on power consumption of mobile device304. Since mobile device power is normally provided by a limited powersource such as a battery, device design and operation must minimizepower consumption in order to extend battery life or the time betweenpower source charging operations when a mobile device includes arechargeable power source.

Wireless link 305 represents one or more different channels, typicallydifferent radio frequency (RF) channels, and associated protocols usedbetween network 302 and device 304. An RF channel is a limited resourcethat must be conserved, typically due to limits in overall bandwidth, aswell as mobile device battery power for example, and may employ avariety of modulation and duplexing schemes. Although a network isnormally adapted to be continuously or intermittently keyed, even if notraffic is exchanged, a mobile device is typically only keyed when ithas traffic to send. Conventional “pull” approaches involving a queryfrom device 304 to network 302 before meaningful information isexchanged between the mobile device and the network, is therefore RFresource intensive and thus unsuitable for many wireless communicationapplications.

Although no network coverage status resolution scheme can improve actualnetwork coverage, it is possible to improve the timeliness in whichtraffic is delivered to a mobile device other than by forcing the mobiledevice to inform the network of its presence relatively often. Broadly,a novel approach for managing network coverage or contact statusinvolves a mobile communication device exploiting particular availableinformation, including predetermined network operation parameters orproperties, and/or measured or detected events, to make an informedestimate of the network's view of the mobile device. If the mobiledevice infers that the network may consider the mobile to be out ofcoverage, then it may transmit a packet or signal to the networkindicating that it is in fact within network coverage. Conversely, ifthe mobile device is able to infer that the network should not havejudged it to be out of range, it may save radio resources by either notindicating its presence to the network or indicating its presence only asmall number of times.

FIG. 2 shows a mobile device state transition diagram in accordance withvarious aspects of the techniques of the instant application. A mobiledevice can hear a base station in all of the states in FIG. 2 except the“temporary coverage loss” state 406 and the “lost, must notify” state408. State 404 represents a mobile device being in good coverage, butnot actively exchanging data with the network. In the event of a loss ofsignal on a network paging channel or similar channel monitored by themobile device, or the strength of such a signal dropping below an RSSI(Received Signal Strength Indicator) threshold, the mobile device willmake a transition 412 from the “good coverage state 404 to a “temporarycoverage loss” state 406. If the signal is regained or improves after ashort period of time, the mobile device may then make a transition 414back to the “good coverage” state 404. Upon regaining network coverageafter a timeout, the mobile device makes a transition 416 to a “lost,must notify” state 408, which is described in further detail below.

In response to a downlink page in the “good coverage” state 404, themobile device makes a transition 418 to an “attempt contact” state 410in which the mobile device attempts to send a response to the network.On successful contact with a base station in the network, the mobiledevice makes a transition 420 to an “exchange traffic” state 402 wherethe base station sends data to the mobile device. The exchanging oftraffic in this state 402 may involve many data packets transferredbetween the mobile device and the network. After exchanging traffic, themobile device makes a transition 422 back to the “good coverage” state404.

The mobile device also has an “in coverage, must notify” state 430. Inthis state 430, the mobile device is listening to the network. Themobile device knows that it must inform the network of its presence, butis holding off for either some time to expire or signal or coverage toimprove. In general, the mobile device spends time in state 430 wheneverpossible rather than in the “lost, must notify” state 408. Conventionalapproaches might dictate that the mobile device be out of coverage untilthe signal is adequate for two-way communications. However, if thesignal is good enough for the mobile to “hear” the network, it can besituated in state 430. To comply with the network, it will not attemptto send to the network while in this state.

From the “lost, must notify” state 408, the mobile device will make atransition 434 to the “in coverage, must notify” state 430 on receivinga signal, no matter how weak, but will make a transition 432 back to the“lost, must notify” state 408 upon losing the signal again. The mobiledevice may also make a transition 436 to the “in coverage, must notify”state 430 from the “attempt contact” state 410 upon failing to contact abase station after receiving a page through a transition 418 (or upon afailure by the network to complete a communication operation), asdescribed in further detail below. In the “in coverage, must notify”state 430, the mobile device makes a transition 438 to the “attemptcontact” state 410 and tries contacting the base station again inresponse to detecting a predetermined condition. The predeterminedcondition may be an expiration of a timeout period, changes in RSSI,detection of a signal as strong as dictated by a network specification,as well as any other cue that it might be a good time to retry tocontact the network, such as user activity or input detected at themobile device.

In most networks, how often and with what interval the network maybroadcast a page message to a mobile device is predetermined. A mobiledevice may thereby monitor a paging channel or equivalent channel on thewireless link and, on not being paged, be certain that the network hasnot attempted to contact it. Thus, even in periods where the signal istoo poor for successful two-way packet exchange to take place, if themobile device determines that no packet exchange was attempted by thenetwork during this time, then the network has no notion that coveragewas poor in the interim, and will not have given up on contacting themobile device.

According to this embodiment, the mobile device remains in the “goodcoverage” state 404 even when coverage is relatively poor, unless nosignal can be decoded. That is, signal quality and signal level do notin themselves cause any transition 412. The transition 412 is thuslimited to situations in which the mobile fails to decode signals fromthe network. Therefore, network update signals that would normally besent from a mobile device when coverage is poor but not lost areavoided. If a page or like signal is detected when the mobile device isin poor coverage, the mobile device will make the transition 418 to the“attempt contact” state 410 and operations continue substantially asdescribed above.

Conversely, if signal strength and quality are good (state 404) and themobile device detects that the network either pages the mobile device orattempts to send traffic to the mobile device (transition 418 to state410), but the network does not complete this communication action, themobile device may infer that the network was unable to decode the mobiledevice's responses. The mobile device thus knows that the network mayhave attempted to send it traffic but was not successful, andsubsequently makes a transition 436 to the “in coverage, must notify”state 430. When certain time, signal condition, or user activityconditions are satisfied, the mobile device will then make a transition438 to the “attempt contact” state 410 and re-inform the network of itspresence. If contact with the network is established, the mobile devicewill make a transition 420 to the “exchange traffic” state 402 and thenetwork will re-attempt sending the traffic. Any traffic will thereby bedelivered to the mobile device in a delayed, but only moderatelydelayed, manner. In accordance with this aspect of the disclosure, themobile device may recognize the problems and can substantially reducethe associated traffic delivery delays.

During periods when the mobile is completely out of touch with thenetwork (state 406), the network may or may not have attempted to reachthe mobile device and judged it to be unreachable. If the mobile deviceis completely out of contact for occasional periods, it is not possiblefor the mobile device to judge whether or not the network may haveattempted to contact it. In packet switched networks, the network mayspend a relatively long time period attempting to contact the mobiledevice before deeming the mobile device to be unreachable. It wasobserved that a Mobitex network, for example, spent hours attempting tocontact a mobile device. In GPRS networks, for example, the time theGPRS components of the network spends retrying is typically muchsmaller, but servers connected to the GPRS network may make it appearmuch longer by doing higher level retries at the IP packet level.

If the characteristics that the network uses in attempting to contact amobile device are known, then this knowledge may be exploited at themobile device. If a control system or software on the mobile deviceknows how long and how often the network may attempt to contact a mobiledevice, even with no response, a judgment can be made as to whether ornot the network may have been able to attempt contact and give up, allduring the period in which the mobile device was not able to hear thenetwork. As such, if the period of time that the mobile device was outof coverage (state 406) was less than the time it takes for the networkto judge the mobile device out of coverage, it is not necessary for themobile device to indicate to the network that it has re-entered coverageafter a period of loss of contact. In accordance with this embodiment,the mobile device preferably remains in the “temporary coverage loss”state 406, and thus may make a transition 414 back to the “goodcoverage” state 404, for significantly longer durations than knownsystems allow.

This general concept can be further extended to include spotty coverage,where the mobile device may compare those time segments of successfulreceipt of a network paging channel against the pattern of pagingrequests usually seen. If and only if the pattern of paging requests canbe fit in such a way that the mobile device may possibly have missedevery paging attempt, then the mobile device should indicate to thenetwork that it is back in coverage. The mobile device may thereforemake a transition 440 to the “in coverage, must notify” state 430 fromthe “good coverage” state 404 when all network paging requests may havebeen missed. To further save power, this can in turn be extended toweigh a risk of missed messages against radio resource usage. Thetransition 440 might therefore be limited to situations in which acumulative probability that the mobile device has missed a message issufficiently high, depending upon the time of day, past trafficpatterns, or other criteria, for example.

Several wireless network update schemes have been described above. Anillustrative example wireless network and mobile communication device inconjunction with which any of the above schemes may implemented will nowbe described in detail with reference to FIGS. 3 and 4. However, theseexamples are intended solely for the purposes of illustration; thenetwork update schemes described herein are in no way restricted to theparticular type of networks or devices described below.

Preferred Network. In this application, the expression “IP basedwireless network” is intended to include, but is not limited to: (1) theCode Division Multiple Access (CDMA) network that has been developed andoperated by Qualcomm; (2) the General Packet Radio Service (GPRS) foruse in conjunction with the Global System for Mobile Communications(GSM) network both developed by the standards committee of the EuropeanConference of Postal and Telecommunications Administrations (CEPT); and(3) future third-generation (3G) networks like Enhanced Data rates forGSM Evolution (EDGE) and Universal Mobile Telecommunications System(UMTS). GPRS is a data communications overlay on top of the GSM wirelessnetwork. It is to be understood that although an IP based wirelessnetwork is shown in FIG. 3, the network update schemes as described inthe present application could be utilized with other types of wirelesspacket data network.

FIG. 3 is a block diagram of a preferred communication system with whicha network update scheme according to the instant application may beimplemented. FIG. 3 shows the basic components of an IP based wirelessdata network, such as the GPRS network. The mobile device 500communicates with a wireless packet data network 545 and may also becapable of communicating with a voice wireless network (not shown), asdescribed in further detail below. The voice network may be associatedwith the IP based wireless network 545, similar to the GSM and GPRSnetworks for example, or may be a completely separate network.

The gateway 540, network entry points 505, name server 507 and addressresolution components 535 are all specific examples of the server 306shown in FIG. 1 and described above. Similarly, the network routers 615in FIG. 3 are examples of a network controller 308 of FIG. 1. Althoughnot explicitly shown in FIG. 3, it will be apparent to those skilled inthe art that the base stations generally designated 520 in FIG. 3include respective base station controllers, and are analogous to thecomponents 310 and 312 of FIG. 1. The GPRS IP based data network isunique in that it is effectively an overlay on the GSM voice network. Assuch, the GPRS components will either extend existing GSM components,such as the base stations 520, or require additional components to beadded, like an advanced gateway GPRS service node (GGSN) as a networkentry point 505.

As shown in FIG. 3, the gateway 540 may be coupled to an internal orexternal address resolution component 535 and one or more network entrypoints 505. Data packets are transmitted from the gateway 540, which isthe source of information to be transmitted to the mobile device 500 inthe example system of FIG. 3, through the network 545 to the mobiledevice 500 by setting up a wireless network tunnel 525 from the gateway540 to the mobile device 500. In order to create this wireless networktunnel, a unique network address must be associated with the mobiledevice. In an IP based wireless network however, network addresses arenormally not permanently assigned to a particular mobile device 500, butinstead are dynamically allocated on an as-needed basis. It is thusnecessary for the mobile device to acquire a network address, and forthe gateway 540 to determine this address so as to establish thewireless network tunnel 525.

A network entry point 505 is generally used to multiplex and demultiplexbetween many gateways, corporate servers and bulk connections like theInternet for example. There are normally very few of these network entrypoints 505, since they are also intended to centralize externallyavailable wireless network services. The network entry points 505 oftenuse some form of address resolution component 535 that assists inaddress assignment and lookup between gateways 545 and mobile devices500. In this example, the dynamic lost configuration protocol (DHCP) isshown as one method for providing an address resolution mechanism.

A central internal component of the wireless data network 545 is anetwork router 515. Normally these network routers 515 are proprietaryto the particular network, but they could instead be constructed fromstandard commercially available hardware. Their purpose is to centralizethe thousands of base stations 520 normally implemented in a relativelylarge network into a central location for a long-haul connection back tothe network entry point 505. In some networks there may be multipletiers of network routers 515, and cases where there are master and slavenetwork routers 515, but in all cases the functions are similar. Oftenthe network router 515 will access a name server 507, in this case shownas a dynamic name server (DNS) 507 as used in the Internet, to look updestinations for routing data messages. The base stations 520, asdescribed above, provide wireless links to the mobile devices 500.

A problem faced by most IP based wireless networks 545 is that theassociated wireless equipment tends to be more complex than atraditional (i.e. wireline) IP network, and includes advancedproprietary hardware that does not normally rely exclusively on IP asthe communication standard. Other protocols for transferring informationover the wireless network 545 may therefore be required. Wirelessnetwork tunnels such as 525 are opened across the wireless network 545in order to allocate the necessary memory, routing and address resourcesto deliver IP packets.

To open the tunnel 525 for example, the mobile device 500 must use aspecific technique associated with the particular wireless network 545.In GPRS, for example, these tunnels 525 are called PDP contexts. Thestep of opening a tunnel may require the mobile device 500 to indicatethe domain, or network entry point 505 with which it wishes to open thetunnel. In this example, the tunnel first reaches the network router515, and the network router 515 then uses the name server 507 todetermine which network entry point 505 matches the domain provided.Multiple tunnels can be opened from one mobile 500 for redundancy or toaccess different gateways and services on the network. Once the domainname is found, the tunnel is then extended to the network entry point505 and the necessary resources are allocated at each of the nodes alongthe way. The network entry point 505 then uses the address resolution(or DHCP 535) component to allocate an IP address for the mobile device500. When an IP address has been allocated to the mobile device 500 andcommunicated to the gateway 540, information can then be forwarded fromthe gateway 540 to the mobile device 500.

The wireless network tunnel 525 typically has a very limited life,depending on the mobile's 500 coverage profile and activity. Thewireless network 545 will tear down the tunnel 525 after a certainperiod of inactivity or out-of-coverage period, in order to recapturethe resources held by this tunnel 525 for other users. The main reasonfor this is to reclaim the IP address temporarily reserved for thatmobile device 500 when the tunnel 525 was first opened. Once the IPaddress is lost and the tunnel is broken down, the gateway 540 thenloses all ability to initiate IP data packets to the mobile device,either over Transmission Control Protocol (TCP) or over User DatagramProtocol (UDP). This general characteristic of IP based wirelessnetworks further illustrates the importance of a mobile device 100 beingable to determine or reasonably judge its status from the network'sview, in accordance with the network update schemes described herein.

Preferred Device. FIG. 4 is a block diagram of a preferred mobilecommunication device which may be configured to inform a network of itsconnection status in accordance with a network update scheme describedin this application. Mobile communication device 610 may be configuredto inform a network of its connection status in accordance with anetwork update scheme of the present application. The mobilecommunication device 610 is preferably a two-way communication devicehaving at least voice and data communication capabilities. The mobiledevice preferably has the capability to communicate with other computersystems on the Internet. Depending on the functionality provided by themobile device, the mobile device may be referred to as a data messagingdevice, a two-way pager, a cellular telephone with data messagingcapabilities, a wireless Internet appliance or a data communicationdevice (with or without telephony capabilities).

Where the mobile device 610 is enabled for two-way communications, themobile device will normally incorporate a communication subsystem 611,including a receiver 612, a transmitter 614, and associated componentssuch as one or more, preferably embedded or internal, antenna elements616 and 618, local oscillators (LOs) 613, and a processing module suchas a digital signal processor (DSP) 620. The communication subsystem 611is analogous to the radio modem 316 and antenna 318 shown in FIG. 1. Aswill be apparent to those skilled in the field of communications, theparticular design of the communication subsystem 611 will be dependentupon the communication network in which the mobile device is intended tooperate. For example, a mobile device 610 may include a communicationsubsystem 611 designed to operate within a Mobitex mobile communicationsystem, a DataTAC mobile communication system, or a GPRS communicationsystem.

Network access requirements will also vary depending upon the type ofnetwork 619 utilized. For example, in the Mobitex and DataTAC networks,such a mobile device 610 is registered on the network using a uniqueidentification number associated with each mobile device. In GPRSnetworks, however, network access is associated with a subscriber oruser of mobile device 610. A GPRS device therefore requires a SubscriberIdentity Module (not shown), commonly referred to as a “SIM” card, inorder to operate on the GPRS network. Without a SIM card, a GPRS devicewill not be fully functional. Local or non-network communicationfunctions (if any) may be operable, but mobile device 610 will be unableto carry out any functions involving communications over network 619.

When required network registration or activation procedures have beencompleted, a mobile device 610 may send and receive communicationsignals over network 619. Signals received by antenna 616 throughnetwork 619 are input to receiver 612, which may perform such commonreceiver functions as signal amplification, frequency down conversion,filtering, channel selection and the like, and in the example systemshown in FIG. 4, analog-to-digital (A/D) conversion. A/D conversion of areceived signal allows more complex communication functions such asdemodulation and decoding to be performed in the DSP 620. In a similarmanner, signals to be transmitted are processed, including modulationand encoding for example, by DSP 620 and input to transmitter 614 fordigital-to-analog (D/A) conversion, frequency up conversion, filtering,amplification and transmission over the communication network 619 viaantenna 618. DSP 620 not only processes communication signals, but alsoprovides for receiver and transmitter control. For example, the gainsapplied to communication signals in the receiver 612 and transmitter 614may be adaptively controlled through automatic gain control algorithmsimplemented in the DSP 620.

Mobile device 610 includes a microprocessor 638, which is oneimplementation of controller 314 of FIG. 1, which controls the overalloperation of the mobile device. Communication functions, including atleast data and voice communications, are performed through thecommunication subsystem 611. Microprocessor 638 also interacts withadditional device subsystems such as a display 622, a flash memory 624,a random access memory (RAM) 626, auxiliary input/output (I/O)subsystems 628, a serial port 630, a keyboard 632, a speaker 634, amicrophone 636, a short-range communications subsystem 640, and anyother device subsystems generally designated as 642.

Some of the subsystems shown in FIG. 4 perform communication-relatedfunctions, whereas other subsystems may provide “resident” or on-devicefunctions. Notably, some subsystems, such as keyboard 632 and display622, for example, may be used for both communication-related functions,such as entering a text message for transmission over a communicationnetwork, and device-resident functions such as a calculator or tasklist.

Operating system software used by the microprocessor 638 is preferablystored in a persistent store such as flash memory 624, which may insteadbe a read-only memory (ROM) or similar storage element (not shown).Those skilled in the art will appreciate that the operating system,specific device applications, or parts thereof, may be temporarilyloaded into a volatile store such as RAM 626. It is contemplated thatreceived communication signals, the detected signal log and the loss ofcontact log may also be stored to RAM 626.

Microprocessor 638, in addition to its operating system functions,preferably enables execution of software applications on the mobiledevice. A predetermined set of applications which control basic deviceoperations, including at least data and voice communication applications(such as a network update scheme), will normally be installed on themobile device 610 during manufacture. A preferred application that maybe loaded onto the mobile device may be a personal information manager(PIM) application having the ability to organize and manage data itemsrelating to the mobile device user such as, but not limited to e-mail,calendar events, voice mails, appointments, and task items. Naturally,one or more memory stores would be available on the mobile device tofacilitate storage of PIM data items on the mobile device. Such PIMapplication would preferably have the ability to send and receive dataitems via the wireless network. In a preferred embodiment, the PIM dataitems are seamlessly integrated, synchronized and updated, via thewireless network, with the mobile device user's corresponding data itemsstored or associated with a host computer system thereby creating amirrored host computer on the mobile device with respect to the dataitems at least. This would be especially advantageous in the case wherethe host computer system is the mobile device user's office computersystem. Further applications may also be loaded onto mobile device 610through network 619, an auxiliary I/O subsystem 628, serial port 630,short-range communications subsystem 640 or any other suitable subsystem642, and installed by a user in the RAM 626 or preferably a non-volatilestore (not shown) for execution by microprocessor 638. Such flexibilityin application installation increases the functionality of the mobiledevice and may provide enhanced on-device functions,communication-related functions, or both. For example, securecommunication applications may enable electronic commerce functions andother such financial transactions to be performed using mobile device610.

In a data communication mode, a received signal such as a text messageor web page download will be processed by communication subsystem 611and input to microprocessor 638, which will preferably further processthe received signal for output to display 622, or alternatively to anauxiliary I/O device 628. A user of mobile device 610 may also composedata items such as email messages, for example, using the keyboard 632,which is preferably a complete alphanumeric keyboard or telephone-typekeypad, in conjunction with display 622 and possibly an auxiliary I/Odevice 628. Such composed items may then be transmitted over acommunication network through communication subsystem 611.

For voice communications, overall operation of mobile device 610 issubstantially similar, except that received signals would be output tospeaker 634 and signals for transmission would be generated bymicrophone 636. Alternative voice or audio I/O subsystems, such as avoice message recording subsystem, may also be implemented on mobiledevice 610. Although voice or audio signal output is preferablyaccomplished primarily through speaker 634, display 622 may also be usedto provide an indication of the identity of a calling party, theduration of a voice call, or other voice call related information, forexample.

The serial port 630 in FIG. 4 would normally be implemented in apersonal digital assistant (PDA)-type communication device for whichsynchronization with a user's desktop computer (not shown) may bedesirable, but is an optional device component. Such a port 630 wouldenable a user to set preferences through an external device or softwareapplication and would extend the capabilities of the mobile device byproviding for information or software downloads to mobile device 610other than through a wireless communication network. The alternatedownload path may for example be used to load an encryption key onto themobile device through a direct and thus reliable and trusted connectionto thereby enable secure device communication. Short-rangecommunications subsystem 640 is a further optional component which mayprovide for communication between the mobile device 624 and differentsystems or devices, which need not necessarily be similar devices. Forexample, subsystem 640 may include an infrared device and associatedcircuits and components or a Bluetooth™ communication module to providefor communication with similarly-enabled systems and devices. Bluetooth™is a registered trademark of Bluetooth SIG, Inc.

FIG. 5 is a flowchart which describes one method of maintaining contactwith a wireless network. The flow chart may involve any of the mobiledevices and/or networks described in relation to FIG. 1, 3, or 4. Themethod of FIG. 5 is a more detailed example of one of the methodspreviously described in relation to FIG. 2. In this description, the useof the term “receiver” may refer to radio modem 316 of FIG. 1 orreceiver 612 of FIG. 4; the term “transmitter” may refer to radio modem316 of FIG. 1 or transmitter 614 of FIG. 4; and the term “processor” mayrefer to controller 314 of FIG. 1 or microprocessor 638 or DSP 620 ofFIG. 4.

Beginning at a start block 702 of FIG. 5, a mobile device uses itsreceiver to monitor a paging channel between the mobile device and thewireless network (step 704). Here, the mobile device preferably operatesin a discontinuous receive mode where the receiver is controlled topower down and wake up in a periodic fashion to listen to broadcastmessage signals in a time slot assigned by the network. While receivingsignals on the paging channel, the mobile device uses its processor todetermine a received signal strength from the signals (step 706) as isconventional. The received signal strength is generally high when themobile device is in a good coverage area, and generally low when themobile device is in a poor coverage area.

With conventional methods, if the received signal strength is too low,the mobile device will reject the current network and “scan” thecoverage area to identify any better signal that can be provided bydifferent base stations or networks. In the present method, however, themobile device continues listening to the network with its receiver andattempting to decode a broadcast message on its paging channel (step708), regardless of the received signal strength. In addition tocontinuing to listen to the network, the mobile device may also scan thecoverage area to identify any better signal from a different networkwhen the received signal strength is low, which is possible in atime-divided communication environment.

Next, the mobile device tests whether the message was successfullydecoded (step 710). This step may be performed in the processor usingany suitable test, conventional or otherwise, such as by examining anerror detection code (e.g. a cyclical redundancy check or CRC), testingfor a checksum error, testing whether the decoded message conforms witha predefined message format, etc. The mobile device may store anindication of whether or not the message was actually decodedsuccessfully, preferably in a decode history list which covers a givenperiod of time.

If the message is successfully decoded as identified in step 710, thenthe mobile device determines whether the message notifies the mobiledevice of an upcoming data communication session (step 712). This step712 may be performed in the processor using conventional techniques,such as by comparing a mobile identification code in the message withthe mobile device's identification code (or temporary identity codeassigned by the network) and, if a match exists, knowing that anupcoming data communication will occur. If the message decoded in step710 does inform the mobile device of an incoming data communicationsession in step 712, then the mobile devices processes the message as isconventional (step 714) (i.e. obtains an assigned traffic channel andthereafter receives data over the traffic channel). When all of the datais received, the mobile device may go back to monitoring a pagingchannel in step 704.

Assuming there was no message directed to the mobile device in step 712,the mobile device identifies whether an inadequate decoding condition ispresent (step 716). If an inadequate decoding condition is present, astested at step 716, then the processor will cause the transmitter of themobile device to transmit an update message which informs the network ofthe mobile device (step 718). An update message is any messagetransmitted by a mobile device that is used to inform and/or update thenetwork of the mobile device's status, even if the message may haveanother different purpose. For, example, the update message may be, inGPRS, a location area update message or a routing area update message.As another example, the update message may be a message for sending userdata. On the other hand, if the adverse decoding condition is notpresent at step 716, the processor will normally refrain from causingthe transmitter to transmit the update message. Typically, no updatemessage will be transmitted in this situation even when the signalstrength is low, as long as most messages are being successfullydecoded. The mobile device may go back to monitoring the paging channelin step 704 to repeat this process.

As apparent, the test in step 716 uses a more intelligent process fortransmitting an update message that is different from just testing thereceived signal strength. The inadequate decoding condition tested instep 716 is determined based on an unsuccessful decoding of one or moreregularly broadcasted messages. Preferably, the condition tested for instep 716 is particularly based on a determination that messagescorresponding to most or all page transmission periods of a networkpaging pattern have been unsuccessfully decoded. In this case, theanalysis may involve the more detailed process described later inrelation to FIGS. 7 and 8(A)-(G).

In a variation to step 718 in FIG. 5, the mobile device transmits theupdate message only when or until communication conditions are deemedadequate (e.g. the received signal strength is above a predeterminedthreshold, and/or one or more messages can be decoded, etc.). In anothervariation, the mobile device delays for a predetermined time periodbefore the transmission of the update message. In yet another variation,the mobile device transmits the update message only when or untilcommunication conditions are adequate after delaying for a predeterminedperiod of time.

As apparent from the method described in relation to FIG. 5, the mobiledevice maintains contact with the wireless network without overburdeningthe wireless link with update messages when the received signal strengthis low. As described, this method involves monitoring a wirelesscommunication channel, determining a received signal strength of signalson the wireless channel, and attempting to decode a message from thesignals. The mobile device normally refrains from transmitting an updatemessage when a message during a page transmission period is successfullydecoded, even though the received signal strength may be below apredetermined threshold. In response to an inadequate decoding conditionbeing identified, however, the mobile device transmits an update messagewhich informs the network of the mobile device. The transmission of theupdate message may be done when communication conditions are deemedadequate, after a predetermined period of time has expired, or both.

FIG. 6 is a flowchart which describes another method of maintainingcontact with a wireless network. The method may involve any of themobile devices and/or networks described in relation to FIG. 1, 3, or 4.The method of FIG. 6 is a more detailed example of one of the methodspreviously described in relation to FIG. 2. In this description, the useof the term “receiver” may refer to radio modem 316 of FIG. 1 orreceiver 612 of FIG. 4; the term “transmitter” may refer to radio modem316 of FIG. 1 or transmitter 614 of FIG. 4; and the term “processor” mayrefer to controller 314 of FIG. 1 or microprocessor 638 or DSP 620 ofFIG. 4.

Beginning at a start block 802 of FIG. 6, a mobile device uses itsreceiver to monitor a paging channel between the mobile device and thewireless network (step 804). Here, the mobile device preferably operatesin a discontinuous receive mode where the receiver is controlled topower down and wake up in a periodic fashion to listen to broadcastmessage signals in a time slot assigned by the network. While monitoringthe paging channel, the mobile device receives signals over the channeland attempts to decode a message from the signals. More particularly,the mobile device uses its receiver and processor to test whether itreceives and decodes a page message which notifies the mobile device ofan upcoming data communication session (step 806). This step may beperformed using conventional techniques, such as by using the processorto compare a mobile identification code in the message with the mobiledevice's identification code and, if a match exists, knowing that anupcoming data communication session will occur for the mobile device.

If the message notifies the mobile device of an incoming datacommunication session in step 806, then the processor will cause a pageresponse message to be transmitted through the transmitter back to thenetwork (step 808). If no response is received back from the networkwithin a short period of time, however, the processor will cause one ormore additional page response messages to be transmitted to the network,in accordance with a conventional or standardized methodology. If anetwork response is eventually received in step 810, then the mobiledevice continues processing the message as is conventional (step 812)(i.e. obtains an assigned traffic channel and thereafter receives dataover the traffic channel). When all of the data is received, the mobiledevice may go back to monitoring a paging channel in step 804.

However, if still no response from the network is received aftertransmitting the page response message(s), as tested at step 810, thenthe processor in the mobile device causes a delay for some period oftime until a predetermined event occurs (step 814). After thepredetermined event occurs as tested at step 814, the processor causesan update message which notifies the network of the mobile device to betransmitted through the transmitter (step 816). An update message is anymessage transmitted by a mobile device that is used to inform and/orupdate the network of the mobile device's status, even if the messagemay have another different purpose. For, example, the update message maybe, in GPRS, a location area update message or a routing area updatemessage. As another example, the update message may be a message forsending user data.

After transmitting this update message, the mobile device waits again toreceive a network response in step 810. If the mobile device receivesthe network response, it may then proceed to complete processing of thepage in step 812. If the mobile device does not receive the networkresponse as tested in step 810, then it continues with the flowchart instep 814 waiting for the predetermined event to occur again as shown.

Alternatively, after transmitting the update message in step 816,instead of waiting for a network response in step 810 the mobile devicemay revert back to monitoring the paging channel in step 804 fordetecting the same (but newly broadcasted) page in step 806. Thereafter,the mobile device again delays until the predetermined event occurs instep 814 to transmit the update message in step 816 and monitor thepaging channel for the page.

In one embodiment, the predetermined event detected in step 814 is anexpiration of a predetermined time period. In this case, thepredetermined time period is preferably between thirty (30) seconds andfive (5) minutes. Such a delay is acceptable for communicationsinvolving updated user data (as opposed to a voice call), such as ane-mail notification for a newly received e-mail message, an e-mailmessage, or updated calendar information. Other time periods suitablefor these data communications may be chosen as well.

In another embodiment, the predetermined event detected in step 814 is adetection of adequate communication quality. The communication qualitymay be based on the received signal strength, for example, or whether ornot messages can be decoded. If the event is based on received signalstrength, then the mobile device waits for the received signal strengthto be above a predetermined threshold value, or for it to be above apredetermined threshold for a predetermined period of time. If the eventis based on whether or not messages can be decoded, the mobile devicedetects when a single message received over the channel is successfullydecoded. Alternatively, the mobile device detects when a plurality ofmessages received over the channel are successfully decoded.

In yet another embodiment, the predetermined event detected in step 814is a detection of user activity at the mobile device. As an example, themobile device may detect any user input at the mobile device, such asthe actuation of a button or touch screen device, before it transmitsthe update message. As another more particular example, the mobiledevice may detect that the end user is attempting to access or open ane-mail application (or calendar application) on the mobile device or attempting to read e-mail information (or calendar information) from themobile device. One or more of these events may be utilized incombination, and other predetermined events providing a suitablemotivation to contact the network may also be utilized.

As apparent from the method described in relation to FIG. 6, the mobiledevice maintains sufficient contact with the wireless network withoutoverburdening the wireless link with update messages when there isinsufficient response from the network. As described, this methodgenerally involves monitoring a wireless communication channel,receiving a message that notifies the mobile communication device of anupcoming data communication session, and transmitting one or moreresponse messages in response to receiving the message. Aftertransmitting the one or more response messages, further communicationsassociated with the message may not be received by the mobile device. Inthis situation, the mobile device will transmit an update message whichinforms the network of the mobile device after it detects apredetermined condition. The predetermined condition may involve anysuitable motivation to contact the network, for example, an expirationof a predetermined time period, a detection of adequate communicationquality, or a detection of user activity at the mobile device.

FIG. 7 is a flowchart which describes yet another method of maintainingcontact with a wireless network. The method may involve any of themobile devices and/or networks described in relation to FIG. 1, 3, or 4.The method of FIG. 7 is a more detailed example of one of the methodspreviously described in relation to FIG. 2. In this description, the useof the term “receiver” may refer to radio modem 316 of FIG. 1 orreceiver 612 of FIG. 4; the term “transmitter” may refer to radio modem316 of FIG. 1 or transmitter 614 of FIG. 4; and the term “processor” mayrefer to controller 314 of FIG. 1 or microprocessor 638 or DSP 620 ofFIG. 4. The method of FIG. 7 exploits what is referred to as a“predetermined paging pattern” that is utilized by the network each timea mobile device is paged to receive data. Before describing theflowchart of FIG. 7 in detail, an example of a predetermined networkpaging pattern is described in relation to a graph shown in FIG. 8(A).

The network is configured and prepared to broadcast the same pagemessage to a mobile device more than once in accordance with the pagingpattern of FIG. 8(A) as the mobile device may be in a poor coverage areaand not be able to receive the page on the first or subsequent tries bythe network. In particular, the predetermined network paging pattern ofFIG. 8(A) includes a plurality of page broadcast periods 1002 eachdesigned by the letter “P” and a corresponding number. In FIG. 8(A), thespecific paging pattern reveals that, each time the network attempts topage a mobile device, it broadcasts a maximum number of six (6) pagemessages over a fifteen (15) second interval, pairing up each two (2)consecutive page message broadcasts with a 0.5 second interval, withseven (7) second delay periods between each page broadcast pair. Moreparticularly, the first message that the network broadcasts is a pagemessage 1004 (P1) shown at a time t₀. About 0.5 seconds later, thenetwork broadcasts another page message 1006 (P2). If the network doesnot receive a page response from the mobile device shortly afterbroadcasting page messages 1004 and 1006, it broadcasts another two pagemessages 1008 and 1010 (P3 and P4) at a time t₇ after a delay of aboutseven (7) seconds. Like page messages 1004 and 1006 (P1 and P2), pagemessages 1008 and 1010 (P3 and P4) are spaced apart by 0.5 seconds. Ifthe network does not receive a page response from the mobile deviceshortly after page messages 1008 and 1010, it broadcasts another twopage messages 1012 and 1014 (P5 and P6) at a time t₁₄ after anotherdelay of about seven (7) seconds. Page messages 1012 and 1014 are alsospaced apart by 0.5 seconds.

If the network does not receive a page response from the mobile deviceshortly after broadcasting page messages 1012 and 1014, the network willaltogether stop broadcasting page messages to the mobile device(assuming no further methodology is employed). In this case, the networkdeems the mobile device “lost” and stops sending it pages. It isdesirable to have the network stop broadcasting page messages to themobile device since it reduces the amount of network traffic over thewireless link; however, this is undesirable when the mobile deviceregains adequate coverage and is able to receive pages.

FIGS. 8(B) and 8(C) show two examples of conventional response scenariosfrom a mobile device after receiving a page from the network. Toillustrate, in FIG. 8(B) it is shown that the mobile device successfullyreceives and decodes the first page message broadcasted by the network(namely, page message 1004 or P1 of FIG. 8(A)) and responds bytransmitting a page response message 1016. Thereafter, a data exchange1018 associated with the page takes place between the mobile device andthe network. In FIG. 8(C), however, it is shown that the mobile deviceinitially has relatively poor coverage 1020 (e.g. over the first nine(9) seconds or so) and therefore misses the initial page messagesbroadcasted by the network (namely, it misses page messages 1004 through1010). However, the mobile device has relatively good coverage after theinitial time period and therefore it receives and decodes a subsequentpage message (namely, page message 1012 or P5 of FIG. 8(A)). Therefore,the mobile device eventually transmits a page response message 1024 and,thereafter, a data exchange 1026 associated with the page takes placebetween the mobile device and the network. In the two scenarios of FIGS.8(A) and 8(B), the system operates as intended and there are no problemsencountered.

To employ the novel aspects of the present disclosure, the mobile devicehas knowledge of the predetermined network paging pattern stored in itsmemory (e.g. RAM, ROM, or EEPROM). The paging pattern may be stored inthe mobile device's memory in any suitable form. For example, the mobiledevice may have the paging pattern of FIG. 8(A) stored in its memory inbinary form as “110000000000001100000000000011” where a binary “1”indicates a broadcasted page message and a binary “0” indicates nobroadcasted page message for a given time period. Although FIG. 8(A)shows a very specific example of a paging pattern employed by a network,any suitable paging pattern may be utilized. Preferably, thepredetermined network paging pattern covers a relatively short period oftime, for example, a predetermined period of time no greater than one(1) minute.

The mobile device utilizes its knowledge of the paging pattern inconnection with what is referred to as a “message decode history list”that is maintained in its memory. The message decode history list is alist of message decode indicators, each of which provides an indicationof whether or not a previous message was successfully decoded over arelatively short period of time (e.g. 0.5 seconds) when one is expected.Put another way, the message decode history list keeps track of whetheror not each of a most recent plurality of regularly broadcasted messageshas been successfully decoded. The list of message decode indicators maytogether cover a relatively long period of time (e.g. the length of theentire predetermined network paging pattern, 15 seconds) from the pastto the present.

The message decode history list and its indicators may be represented inany number of different ways. For example, each message decode indicatormay indicate either a “MESSAGE SUCCESSFULLY DECODED” (‘1”) condition ora “MESSAGE NOT SUCCESSFULLY DECODED” (‘0’) condition for the period oftime. In this case, the message decode history list may be representedin binary form, for example, as “111011111111111011111101111111”, whereeach binary number corresponds to a period of 0.5 seconds for a totaltime period of 15 seconds, the leftmost binary number being the leastrecent time period and the rightmost number being the most recent timeperiod. Thus, these indicators are preferably stored in temporal orderfrom left to right. In this specific example, the history list shownindicates relatively good decoding over the fifteen (15) second timeperiod within only three (3) short intervals (where the three binary “0”numbers are located) where decoding was poor. As apparent, the messagedecode history list covers a time period that is equal to or greaterthan the entire predetermined network paging pattern.

The mobile device generates the message decode history list using itsreceiver to monitor the paging channel established between the mobiledevice and the wireless network. While monitoring the paging channel,the mobile device performs various tasks including receiving signalsover the channel, determining the received signal strength of thesignals, and attempting to decode a message from the signals. The mobiledevice determines a message decode indicator based on whether or not anexpected broadcasted message was decoded over the period of time. Moreparticularly, if the broadcast message was decoded over the period oftime, then the message decode indicator is marked as successful(“MESSAGE SUCCESSFULLY DECODED” or “1”); if the broadcast message wasunable to be decoded over the period of time, then the message decodeindicator is marked as unsuccessful (“MESSAGE NOT SUCCESSFULLY DECODED”or “0”). After determining the current message decode indicator, themobile device causes it to be stored in the message decode history listas the most recent entry.

Use of the message decode history list and the stored network pagingpattern will now be described in relation to the flowchart of FIG. 7.Beginning at a start block 902 of FIG. 7, the mobile device maintains amessage decode history list in its memory (step 904). The maintenance ofthe history list may include using the processor and memory tocontinually maintain storage of the list and update the message decodeindicators to reflect the current time period. The maintenance of thelist may also include deleting relatively “old” decode indicators. Asone example, if the history list is maintained in binarytemporally-ordered form as described earlier, it may be preferable toperiodically utilize a “logical shift left” or equivalent operation onthe list to simultaneously add the most recent message decode indicatorand remove the oldest one.

Next, the mobile device uses its processor to compare the message decodehistory list with the predetermined network paging pattern stored in itsmemory (step 906 of FIG. 7). The predetermined network paging patternmay be that described above in relation to FIG. 8(A), for example. Inthis comparison, the time periods in the list and the pattern areproperly aligned to order to identify the overlap between poor/gooddecode periods and the page transmission/non-transmission periods. Themobile device then uses its processor to test whether one or moreunsuccessful message decode periods in the message decode history listoverlap with all page transmission periods in the paging pattern (step908). If this is the case, the mobile device may have missed a page fromthe network so therefore it transmits an update message which informsthe network of the mobile device (step 910), and may repeat the methodstarting at step 904. An update message is any, message transmitted by amobile device that is used to inform and/or update the network of themobile device's status, even if the message may have another differentpurpose. For, example, the update message may be, in GPRS, a locationarea update message or a routing area update message. As anotherexample, the update message may be a message for sending user data.

If the one or more unsuccessful message decode periods do not overlapwith all page transmission periods in the pattern (i.e. if anysuccessful message decode indicator in the history list overlaps withany page transmission period of the paging pattern) as tested in step908, the mobile device normally refrains from transmitting an updatemessage to the network. The method may be repeated starting again atstep 904.

In an alternative embodiment of FIG. 7, the mobile device transmits theupdate message only when communication conditions are deemed adequate(e.g. the received signal strength is above a predetermined threshold,and/or one or more messages can be decoded, etc.). In another alternateembodiment, the mobile device delays for a predetermined time periodbefore the transmission of the update message. In yet another alternateembodiment, the mobile device transmits the update message only whencommunication conditions are adequate after delaying for a predeterminedperiod of time.

If the history list and paging pattern data is maintained in binaryform, steps 906 and 908 of FIG. 7 may be performed using a logical “AND”operation between the list and the pattern. For example, a logical ANDoperation of the paging pattern of “110000000000001100000000000011” andthe history list of “111011111111111011111101111111” provides a non-zeroresult which indicates that at least one successful message decodeperiod co-existed with a potential page message broadcast by thenetwork. A logical AND operation of the same paging pattern“110000000000001100000000000011” and the history list of“000010101000000000000111000000” provides a result of zero whichindicates that no successful message decode period co-existed with apotential page message broadcast by the network. In the latter case, themobile device transmits an update message which informs the network ofthe mobile device; in the former case, it normally does not. As oneskilled in the art will readily understand, other suitable logicaloperations may be utilized to achieve the same results.

In another alternate embodiment of FIG. 7, the mobile device requires agreater number of successful message decode periods to overlap with pagemessage broadcast periods to refrain from transmitting the updatemessage. That is, more than one successful message decode period isrequired to overlap with more than one potential page transmission bythe network. For example, the mobile device may require that two orthree successful message decode periods overlap with two or threepotential page message broadcast periods to order to refrain fromtransmitting the update message. In this case, any number less than twoor three will result in the update message being transmitted by themobile device.

FIGS. 8(D) through 8(G) show various examples of possible responses froma mobile device with use of the methodology described in relation toFIGS. 7 and 8(A). In FIGS. 8(D) through 8(G), the mobile device isoperating in relatively poor coverage and the network has not attemptedto broadcast any page messages to the mobile device. FIGS. 8(D)-(E)reveal scenarios where the coverage area was indeed poor enough totransmit an update message to the network, whereas FIGS. 8(F)-(G) revealscenarios where transmission of an update message was not deemednecessary.

More particularly, FIG. 8(D) shows that the mobile device operated in arelatively poor coverage period 1028 over an extended period of time(e.g. over 15 seconds). Thus, all of the message decode indicators inthe message decode history list maintained by the mobile deviceindicated poor coverage over this period 1028 (i.e. list is“000000000000000000000000000000”). In response to the comparison of thehistory list and the network paging pattern, the mobile stationtransmits an update message 1032 which informs the network of the mobiledevice during a relatively good coverage period 1030. The mobile stationtransmits the update message 1032 even though the network may not havebroadcasted any page message during period 1028.

FIG. 8(E) shows that the mobile device operated in a fringe area whereboth poor and good coverage conditions were encountered. As shown inFIG. 8(E), the mobile device experienced a plurality of poor coverageperiods 1036, 1040, and 1044 as well as a plurality of good coverageperiods 1038, 1042, and 1046. This caused the mobile device to transmitan update message 1048. The message decode history list may haverepresented this time period in binary form as“000000111111110000001111111100” in accordance with FIG. 8(E).Performing a logical “AND” operation with this history list and thepaging pattern of “110000000000001100000000000011”, a result of zero isprovided which causes the update message to be transmitted. The mobilestation transmits the update message 1048 even though the network maynot have broadcasted any page message during the period of marginalcoverage.

FIG. 8(F) shows that the mobile device operated in another fringe areawhere both poor and good coverage conditions were encountered. As shownin FIG. 8(F), the mobile device experienced a plurality of poor coverageperiods 1052 and 1056 as well as a plurality of good coverage periods1054 and 1058. However, the mobile device refrained from transmitting anupdate message. The message decode history list may have representedthis time period in binary form as “000000111111000000000000000011” inaccordance with FIG. 8(F). Performing a logical “AND” operation withthis history list and the paging pattern of“110000000000001100000000000011”, a non-zero result is provided whichcauses the mobile device to refrain from transmitting an update message.

FIG. 8(G) shows that the mobile device operated in yet another fringearea where both poor and good coverage conditions were encountered. Asshown in FIG. 8(G), the mobile device experienced a plurality of poorcoverage periods 1052 and 1056 as well as a plurality of good coverageperiods 1054 and 1058. However, the mobile device refrained fromtransmitting an update message. The message decode history list may haverepresented this time period in binary form as“000000000000111100000000000000” in accordance with FIG. 8(G).Performing a logical “AND” operation with this history list and thepaging pattern of “110000000000001100000000000011”, a non-zero result isprovided which causes the mobile device to refrain from transmitting anupdate message.

As apparent from the method described in relation to FIGS. 7 and8(A)-8(G), the mobile device maintains sufficient contact with thewireless network without overburdening the wireless link with updatemessages when coverage is marginal. As described, this method involvescontinually maintaining a message decode history list and comparing itwith a predetermined paging pattern of the network. An update messagewhich informs the network of the mobile device is transmitted inresponse to identifying that one or more unsuccessful message decodeperiods in the message decode history list overlap with all pagetransmission periods in the predetermined network paging pattern. On theother hand, the update message is not normally transmitted in responseto identifying that any successful message decode period in the messagedecode history list overlaps with any page transmission period in thepredetermined network paging pattern. Preferably, the mobile deviceutilizes a combination of one or more (or all) of the contact managementschemes described herein. It will be appreciated that the abovedescription relates to preferred embodiments by way of example only.Many variations on the techniques will be obvious to those knowledgeablein the field, and such obvious variations are within the scope of theinvention, whether or not expressly described.

1. A method in a mobile communication device for communicating in awireless communication network, the wireless communication networkhaving a predetermined network paging pattern comprising a plurality ofpage transmission periods during which repeated attempts for initiatinga communication with the mobile communication device are made, themethod comprising the acts of: attempting to decode information over awireless communication channel during each one of the page transmissionperiods; if the information is unsuccessfully decoded during all of thepage transmission periods: causing a message which informs the networkof the mobile communication device to be transmitted to the wirelesscommunication network; and if the information is successfully decodedduring at least some, but not all, of the page transmission periods:refraining from transmitting the message to the wireless communicationnetwork.
 2. The method of claim 1, further comprising: continuallyrepeating the recited acts for additional page transmission periods. 3.The method of claim 1, further comprising: delaying the transmission ofthe message until communication conditions are adequate.
 4. The methodof claim 1, wherein the act of refraining from transmitting the messageto the wireless communication network is performed if the information issuccessfully decoded during only one of the page transmission periods.5. The method of claim 1, further comprising: If the information issuccessfully decoded during all of the page transmission periods:refraining from transmitting the message to the wireless communicationnetwork.
 6. The method of claim 1, further comprising: maintaining amessage history decode list to track, for each page transmission periodof the predetermined network paging pattern, whether the information hasbeen successfully decoded; and determining whether to transmit orrefrain from transmitting the message based on the message historydecode list.
 7. The method of claim 1, further comprising: continuallymaintaining and updating a message history decode list to track, foreach page transmission period of the predetermined network pagingpattern over a current time period, whether the information has beensuccessfully decoded; and determining whether to transmit or refrainfrom transmitting the message based on the message history decode list.8. The method of claim 1, wherein the wireless communication channelcomprises a broadcast channel and the information comprises broadcastmessage information of a broadcasted message.
 9. The method of claim 1,wherein the wireless communication channel comprises a broadcast channelover which page messages are broadcasted, and the act of attempting todecode the information comprises page message information.
 10. Themethod of claim 1, further comprising: decoding information in one ofthe page transmission periods; and if the information indicates acommunication intended for the mobile communication device: receivinginformation for the communication.
 11. The method of claim 1, furthercomprising: powering down a receiver of the mobile communication deviceduring periods other than the page transmission periods.
 12. The methodof claim 1, which reduces power consumption in the mobile communicationdevice, reduces traffic in the wireless communication network, or both.13. The method of claim 1, which is embodied in a computer programproduct comprising a computer readable medium and computer instructionsstored in the computer readable medium, wherein the computerinstructions are executable by one or more processors in the mobilecommunication device for performing the method.
 14. A mobilecommunication device operative to communicate in a wirelesscommunication network, the wireless communication network having apredetermined network paging pattern comprising a plurality of pagetransmission periods during which repeated attempts for initiating acommunication with the mobile communication device are made, the mobilecommunication device comprising: a receiver; a transmitter; an antennacoupled to the receiver and the transmitter; one or more processorscoupled to the receiver and the transmitter; the one or more processorsbeing operative with the receiver and the transmitter to: attempt todecode information over a wireless communication channel, via thereceiver, during each one of the page transmission periods; if theinformation is unsuccessfully decoded during all of the pagetransmission periods: cause a message which informs the network of themobile communication device to be transmitted to the wirelesscommunication network via the transmitter; and if the information issuccessfully decoded during at least some, but not all, of the pagetransmission periods: refrain from transmitting the message to thewireless communication network via the transmitter.
 15. The mobilecommunication device of claim 14, wherein the one or more processors arefurther operative to: continually repeat the recited actions foradditional page transmission periods.
 16. The mobile communicationdevice of claim 14, wherein the one or more processors are furtheroperative to: delay the transmission of the message until communicationconditions are adequate.
 17. The mobile communication device of claim14, wherein the one or more processors are further operative to refrainfrom transmitting the message to the wireless communication network ifthe information is successfully decoded during at least one of the pagetransmission periods.
 18. The mobile communication device of claim 14,wherein the one or more processors are further operative to: If theinformation is successfully decoded during all of the page transmissionperiods: refrain from transmitting the message to the wirelesscommunication network via the transmitter.
 19. The mobile communicationdevice of claim 14, wherein the one or more processors are furtheroperative to: maintain a message history decode list to track, for eachpage transmission period of the predetermined network paging pattern,whether the information has been successfully decoded; and determinewhether to transmit or refrain from transmitting the message based onthe message history decode list.
 20. The mobile communication device ofclaim 14, wherein the one or more processors are further operative to:continually maintain and update a message history decode list to track,for each page transmission period of the predetermined network pagingpattern over a current time period, whether the information has beensuccessfully decoded; and determine whether to transmit or refrain fromtransmitting the message based on the message history decode list.
 21. Acommunication system comprising: a wireless communication network; aplurality of mobile communication devices operative in the wirelesscommunication network; the wireless communication network beingoperative to initiate a communication with a mobile communication devicein accordance with a predetermined network paging pattern, thepredetermined network paging pattern comprising a plurality of pagetransmission periods during which repeated attempts for initiating thecommunication with the mobile communication device are made; at leastone of the mobile communication devices being operative to: attempt todecode information over a wireless communication channel during each oneof the page transmission periods; if the information is unsuccessfullydecoded during all of the page transmission periods: cause a messagewhich informs the network of the mobile communication device to betransmitted to the wireless communication network; and if theinformation is successfully decoded during at least some, but not all,of the page transmission periods: refrain from transmitting the messageto the wireless communication network.
 22. The communication system ofclaim 21, wherein the mobile communication device is further operativeto: continually repeat the recited actions for additional pagetransmission periods.
 23. The communication system of claim 21, whereinthe mobile communication device is further operative to: delay thetransmission of the message until communication conditions are adequate.24. The communication system of claim 21, wherein the mobilecommunication device is further operative to: refrain from transmittingthe message to the wireless communication network if the information issuccessfully decoded during at least one of the page transmissionperiods.
 25. The communication system of claim 21, wherein the mobilecommunication device is further operative to: If the information issuccessfully decoded during all of the page transmission periods:refrain from transmitting the message to the wireless communicationnetwork.